The present invention relates to spill containment systems for storage or flow means, such as for at least one storage tank, for light and/or dense non-aqueous phase liquid, as well as to a containment system for spilled light non-aqueous phase liquid.
Leaking storage tanks that contain light non-aqueous phase liquids (LNAPLs), such as gasoline, diesel or jet fuel, heating oil, etc. have been and remain an expensive and ubiquitous environmental problem. Free-phase LNAPL is very difficult and expensive to remove from contaminated aquifers. In fact, a recent realization in the environmental industry is that removal of all of an aquifer""s contaminants may not be possible or, at least, may not be practical from a stand point of limited economic resources. One gallon of free-phase LNAPL can contaminate almost 1 million gallons of ground water. Therefore, containment of free-phase LNAPL is of major importance in preventing the risk of significant environmental degradation due to LNAPL spills. A secondary trapping system for free-phase LNAPLs installed around underground storage tanks and beneath surface tanks and around tank farms would essentially prevent off-site contamination by free-phase LNAPLs.
The state of California currently requires liners and French drains below underground storage tanks to contain spills. However, such a design suffers from a fatal flaw when used with light non-aqueous phase liquids, which are less dense than water, because when the liner overflows during heavy rain storms or floods, or due to water system leaks, the spilled gasoline, etc. will simply float out of the liner and enter and contaminate the surrounding aquifer or soil.
U.S. Pat. No. 5,421,671, Lewis, discloses a containment system that requires several monitoring wells as well as horizontal or sub-horizontal drains. Unfortunately, the Lewis system cannot trap and remove free-phase LNAPL without having to pump water from the system as well. The Lewis system is also unable to handle situations when the containment structure is flooded or otherwise washed down with water. U.S. Pat. No. 5,575,585, Kovarak, discloses an apparatus for remediating already spilled contaminants. This apparatus, which uses several angled wells drilled out of the base of a pit and into contaminated ground water, is designed to clean up previously spilled contaminants and not for containing spills from storage tanks. This patent does not provide any LNAPL traps. U.S. Pat. No. 4,543,013, Wagner et al, discloses a system placed below surface water impoundments such as open pits or lagoons to treat contaminated water leaking from the overlying pit. The treated leakage is then collected and removed. This system is not designed for collection and removal of floating LNAPLs. U.S. Pat. No. 3,516,568, Fish, discloses a system for storing liquids using a flexible walled tank suspended in liquid. Again, no provision is made for the collection and removal of LNAPLs.
It is an object of the present invention to provide an economical and effective system for catchment or containment of surface and sub surface spills of light non-aqueous phase liquids from tanks or the like.